The invention generally relates to a hydrostatic displacement engines such as radial piston engines (pump or motor) or vane engines (pump or motor). More particularly, the invention pertains to a hydrostatic displacement engine in which a rotating cylinder block contains several radially shiftable displacement elements that slide on a stroke ring.
Prior engines of this type have been described, e.g., in the following documents:
German patent disclosure 35 45 019,
German patent disclosure 37 00 573.
The radial piston pump known from the German patent disclosure 35 45 019 has a rotatable cylinder block which is mounted on a stationary control journal. This journal is situated in a housing whose interior is sealed by a housing cover. Contained in the cylinder block are several radially movable pistons which, by way of a piston shoe each bear on the inside of a stroke ring. Although not immediately evident from the German patent disclosure, the stroke ring is movable transverse to the axis of rotation of the cylinder block in order to change the stroke of the piston. All areas of the housing interior, i.e., those areas situated within and outside the stroke ring, are connected with one another and connected with a low-pressure area (for instance in the form of a liquid container) by means of a leakage oil outlet.
Radial piston engines of this design (working either as a pump or as a motor) and the vane engines operating according to a similar principle have been proven in practice. A problem with these displacement engines, however, is the noise which is occasionally experienced in their operation, and in particular the frequently observed change of noise. The noise intensity assumes elevated levels especially when the stroke ring is contained in an intermediate position, i.e., when the stroke ring bears on neither of its two limit stops.
The problem underlying the invention is to introduce measures by which the operationally caused noise in the aforementioned hydrostatic displacement engines will be reduced, especially in an intermediate position of the stroke ring.